The party didn't "install" him. He got elected in an R+22 state as a former governor with excellent rapport and name recognition. He's just about the only "Democrat" who could be elected in a blood red coal mining state. If the party abandoned their approach and threw their weight behind someone more left-leaning, they'd be absolutely clobbered and we'd all be hemming and hawing about WV being a total loss Republican wasteland for the next few generations. At least this way we get someone who's willing to confirm judges and meet with the party behind closed doors.
edit: Not to mention the event he's skipping is to celebrate the most aggressive climate/clean energy legislation in the history of this country. And he's campaigning in a coal mining state. That'd be like a Ukrainian general attending a dinner party with the Kremlin. NOT a good look.